Captured on camera as they’re about to break the surface of the water, some Olympic swimmers seem to be perfectly wrapped in glass or clear gel, because of a physical phenomenon called surface tension.
It’s the tendency of liquid surfaces to shrink into the minimum surface area possible. The same force allowing insects — e.g. water striders — to float and slide on a water surface, without becoming even partly submerged. Because of the relatively high attraction of water molecules to each other through a web of hydrogen bonds, water has a higher surface tension — 72.8 millinewtons per meter at 20 °C — than most other liquids.